Systems and storage modules for packaging nuclear waste are known in the prior art. One such known storage module is formed as a precast modular concrete container within which waste packages are placed. The module is about two meters in diameter, which renders it small enough to be handled by a shielded forklift, and has hexagonal walls so that is may be efficiently stacked into a solid array at a disposal site. Typically, the storage module is closed off by a precast concrete lid and the module is then transported to a storage repository or disposal site. An example of a storage facility utilizing such precast storage modules is shown in U.S. Pat. No. 4,681,706 issued Jul. 21, 1987, and owned by the Westinghouse Electric Corporation. The disclosure of U. S. Pat. No. 4,681,706 is expressly incorporated by reference herein.
In the past, a cementitious grout has been poured within the storage module to secure the waste packages in place and also to provide an additional leakage barrier and radiation shield. A granular fill material, which is the subject matter of commonly owned U.S. Pat. No. 4,950,426, entitled "Granular Fill Material for Nuclear Waste Containing Modules" filed March 31, by Joseph M. Markowitz et al. and also assigned to the Westinghouse Electric Corporation is even more preferred for this purpose. For low level and short level radioactive wastes, such additional leakage barrier layers, being either a cementitious grout or granular fill, are normally amply sufficient for most storage purposes.
However, for long-lived radionuclides, high-level radioactive waste, and mixed waste, the additional protection afforded by an impermeable liner placed within the storage module is highly desirable. Radioactive waste can remain as a hazardous material for 200 years or more, depending on the known half lives of the specific radioactive elements. Therefore, it is necessary that the storage containers be sufficiently strong and durable to provide a leak-tight barrier for as many years.
A known liner used for additional protection in the previously described concrete storage module has been manufactured by welding together pieces of an impermeable material along the internal sidewalls of the container. While such a liner is capable of providing a durable leak-tight barrier, it is unfortunately difficult to fabricate and to install. Because of manufacturing tolerances, the inside diameter of the storage modules vary and the sections of the liner to be pieced together also vary. As a result of these variances, it is difficult to obtain a precise fit between the liner and the interior of the concrete module without custom-modifying the dimensions of the liner sections, which is time consuming. The installation of such a liner results in a loss of storage space within a module, even when the fit is perfect. Finally, because the liner includes a number of weld joints, there is a possibility that the welds can fail thus providing a path for liquid waste to leak out of the container.
Another example of a lined concrete container is disclosed in U.S. Pat. No. 4,458,458 issued Jul. 10, 1984 to Orii. In this patent, a concrete tank is lined by plates which are attached to the inside surfaces of the tank. In each of the disclosed embodiments, however, the lining plates are either welded to an embedded member within the concrete walls, or to each other where they abut adjacently. Thus, the same problems associated with welding of a liner, are still present in such a device.
Clearly a need exists for a storage module of precast concrete for storing nuclear wastes that has the additional protection of an impermeable liner placed within it that eliminates the manufacturing problems of fitting the liner into the concrete module, and does not result in the loss of any significant amount of storage space. Ideally, such a liner should not have any welded joints which could fail and provide a leakage path through the container.